Alkylation effluent flash vaporization system



O. WEBB, JR

Sept. 25, 1962 ALKYLATION EFFLUENT FLASH VAPORIZATION SYSTE J 1 X 1 .N m.\ RN m M m QQ W W w k xw wu NW W f 4 m w S O 4 *Q\ \N M g Filed July 16, 1958 0. WEBB, JR

Sept. 25, 1962 ALKYLATION EFFLUENT FLASH VAPORIZATION SYSTEM 0. WEBB, JR

Sept. 25, 1962 ALKYLATION EFFLUENT FLASH VAPORIZATION SYSTEM A 770 NEK 0. WEBB, JR

Sept. 25, 1962 ALKYLATION EFFLUENT FLASH VAPORIZATION SYSTEM Filed July 16, 1958 4 Sheets-Sheet 4 IN V EN TOR. Or/ando h eb 4/4 A TZ NEV.

United States Patent 3,955,958 ALKYLATIGN EFFLUEl "l FLASH VAPORIZATION SYSTEM Orlando Webb, Jr., Prairie Village, Kans, assignor to Stratford Engineering Corporation, Kansas City, M0., a corporation of Delaware Filed July 16, 1953, Ser. No. 748,833 Claims. (Cl. 260-68358) This invention relates to improvements in processes of alkylating isoparafiinic hydrocarbons with olefinic hydrocarbons in the presence of acid catalysts and an excess of isoparaifinic hydrocarbons and refers more particularly to methods for reducing the load in such processes on the step of retrieving the excess isoparaffinic hydrocarbons from the alkylation reaction effluent for recycle to the reaction step.

Many conventional methods and processes are known, and employed. Varying more or less from one another, wherein isobutane is alkylated with olefins in the presence of sulphuric acid or other acid catalyst and an excess of isobutane. Various types of reaction vessels may be employed in these various processes. The reaction steps of the various processes may or may not be heat exchanged to control the reaction temperatures. If the reaction is heat exchanged, efiiuent refrigeration may or may not be employed. In all of the conventional alkylation processes, however, whatever the specific arrangements for conducting the reaction may be once the catalyst phase has been separated from the hydrocarbon phase of the eliiuent from the reaction step, the hydrocarbon component is passed to various stages of fractionation where alkylate is separated from excess isoparaifinic hydrocarbons, so the latter may be recycled as feed to the reaction step to aid in the maintenance of a large proportional excess of isobutane.

The equipment involved in such separation usually includes a deisobutanizer tower of great expense and size. For example, an 8,000 barrel per day deisobutanizer tower has a cost of presently in excess of $400,000.00. In view of such great cost, it is desirable to reduce the size of the deisobutanizer tower as much as possible. However, any change in this direction lies directly in the face of one of the most important functions of the fractionation system, namely, to return as much isobutane as possible to the reaction step to maintain the optimum reaction conditions and avoid deterioration of the alkylate product.

Therefore, an object of the invention is to provide means and method for reducing the load on both newly constructed an existing alkylation fractionation systems, in that, the deisobutanizer towers of newly constructed alkylation systems may be of markedly reduced size without reducing the quantity of isobutane recycled to the reaction, and wherein the alkylate capacities of already existent alkylation systems may be greatly increased without, again, reducing the quantity of isobutane recycled to the reaction step.

Another object of the invention is to provide such means and methods for reducing the load on the alkylation fractionation systems which are of great simplicity, involve a minimum of expense to apply and, also, a minimum of plant redesign.

Another object of the invention is to provide means and methods for reducing the load on deisobutanizer ,towers in alkylation fractionation systems which may be applied to any existent alkylation system, independently of the type of reaction vessel employed in the reaction step, whether or not the reaction step is heat exchanged, or how the reaction step is heat exchanged.

Yet another object of the invention is to provide means and methods for reducing the load on deisobutanizer towers of alkylation fractionation systems in combined alkylation systems utilizing varied and interdependent heat exchanging systems for the reaction steps, said means and methods as applied being simple in construction, design and relatively inexpensive.

Other and further objects of the invention will appear in the course of the following description thereof.

In the drawings, which form a part of the instant specification and are to be read in conjunction therewith, embodiments of the invention are shown in the form of schematic flow diagrams illustrating a variety of ialkylation systems and processes.

FIG. 1 is a schematic flow diagram illustrating an auto-refrigerated form of alkylation system employing the inventive improvement.

FIG. 2 is a schematic flow diagram showing an alkylation system wherein the reaction step is heat exchanged by a closed cycle refrigeration system employing the inventive improvement.

FIG. 3 is a schematic flow diagram of an alkylation system utilizing varied forms of eflluent refrigeration to cool the reaction step employing the inventive improvement.

FIG. 4 is a schematic flow diagram showing alkylation systems and processes embodied in combined reactors where one of the reactors is heat exchanged by a closed cycle refrigeration system and the second reactor is refrigerated by an effluent refrigeration system, the systems employing the inventive improvement.

Referring to FIG. 1 therein is shown the inventive improvcment in combination with an auto-refrigerated oascade-type reactor installation. At 10 is shown the reactor vessel with height graded bafiles 11, 12, 13 and 14 defining a series of cascade flow chambers 11a, 12a, and 14a therein. Mixers 15, 16 and 17 agitate the liquid contents of the chambers. Flow line 18 inputs acid catalyst to chamber 11. Fresh isobutane is input to the system through line 19. The fresh isobutane is input to the chamber 11a through line 20. Recycle isobutane goes into the chamber 11a through line 21. Olefin is input to the system through line 22 which line is split into subsidiary lines 23, 24 and 25 into the chambers 11a, 12a and 13a. The alkylation reaction takes place in the first three chambers with evolution of vapors of isobutane withdrawn from fitting 26 at the top of the vessel 10 through line 27. In chamber 14a, the acid settles and is taken out the bottom of the vessel through line 28. The spill over of hydrocarbon effluent from chamber 14a is taken off the bottom of the vessel through fitting 29 and line 30. The isobutane vapors taken off through line 27 pass to compressor 31 then through line 32 to condenser 33 and from the condenser through line 34 to accumulator 35. Line 36 joins input line 19 where the recycle isobutane vapors and fresh isobutane go through valve 37 and into the vessel.

The hydrocarbon effluent from the chamber between the end wall of the reactor and baflie 14 passes through line 30 to pump 38 then through line 40 to heat exchanger 39 and through line 41 to the conventional neutralization and water wash step of an akylation system schematically shown at 42. Heat exchanger 39 cools the olefin input through line 22. From the neutralizer 42, the hydrocarbon efiluent passes through line 43 through heat exchanger 44 where it is heated by the steam passing therethrough in line 45 and from thence through line 46 to eflluent flash drum 47. Line 48 from the top of the eflluent flash drum takes the vapors of isobutane evolved from the heat applied through the heat exchanger 44 and passes them to condenser 49 and thence through line 50 to accumulator 51. From the accumulator, the condensed isobutane is passed through line 52 and pump 53 into feed line 21 which goes to the first reaction chamber in the reaction vessel to increase the isobutane concentration there.

t 42 take place 'culating head and Line 54 from effluent flash drum 47 passes to the deisobutanizer tower 55. Normal butane, alkylate and heavier hydrocarbons that may have been charged to the unit as part of the feed stock are Withdrawn from the deisobutanizer through line 56 while the isobutane and other parafiinic hydrocarbon vapors are taken overhead through line 57 to condenser 58, line 59 and accumulator 60. From the accumulator, line 61 passes to pump 62 and thence into recycle line 63 which joins new isobutane input line 19.

By means of the provision of the heat exchanging step at exchanger 44 and the flash drum 47 which re cycles isoparaffinic vapors through condenser 49 and accumulator 51 back to the first reaction chamber in the vessel 10, I permit either initial reduction of the size of the deisobutanizer tower in a new system or greater capacity of an existent system of this type already having a deisobutanizer tower of a given size. While it is preferable that the neutralization and water washing step before the effluent flash, such is not necessary. Accumulator 51 and/or pump 53 may not be necessary in some installations as in almost all cases the operating pressure of the eflluent flash drum will be high enough to force the condensate back to the reactor without requiring a pump.

In the type of reaction vessel of FIG. 1, an important process equilibrium exists in the last compartment of the reactor. This equilibrium is affected by the olefin concentration in the acid in the last compartment and the isobutane concentration of the hydrocarbon liquid with which it is in contact. Since vaporization takes place direcly from the reaction zones (chambers 11a, 12a and 13a) in this arrangement, the only isobutane available to increase the concentration of isobutane in the liquid in contact with the catalyst is that which leaves the reactor as liquid effluent through line 30. Using a given deisobutanizer tower and a given quantity of deisobutanizer overhead recycle, the effluent flash vaporization system shown may be used to accomplish a considerable increase in the isobutane concentration at the point of final equilibrium in the reactor with the result that the yield and quality of the alkylate product will be increased.

Referring now to FIG. 2, the numbering of this figure will start with 70 to avoid confusion with the preceding system. At 70 is shown a reaction vessel having an outer shell with a circulating tube 71 spaced inwardly from the outer shell and open at both ends to communicate with a space in the vessel. Impeller 72 is positioned in one end of the circulating tube and is driven by shaft 73 attached to motor or other prime mover 74. Heat exchanging tube bundle 75 comprises U-bends of tubing which are rolled into tube sheet 76. Header 77 has baffle 78 dividing its volume. Input and output connections 79 and 80 are positioned on the header and lead into the separated volumes. Heat exchanging medium pasing through fitting 79 goes into one side of the header through the tubing and out the other side of the header through fitting 80. The path of fluids in the reactor is through the center of the circulating tube from the heat exchanging tube bundle toward the impeller, into a cirout between the outside surface of the circulating tube 71 and the inside surface of the reactor shell 70.

The refrigeration system for reactor 70' is a closed cycle one wherein the heat exchanging medium is input to the header 77 through line 81, taken ofi through line 82 then passed to compressor 83, from thence through line 84 to condenser 85 and from the condenser through line 86 to accumulator 87.

Isobutane is fed into the system through line 88 which joins main feed line 89 to the reactor 70. Olefin is input to the system through line 90, is heat exchanged and input to the reactor through line 91. In the re actor, the isoparaflinic hydrocarbons are alkylated with olefinic hydrocarbons in the presence of an acid catalyst and the effluent alkylate, excess isoparaffinic hydrocarbons and acid are withdrawn through line 92 and passed to settler 93 Acid is withdrawn from the settler through line 94, acid passed out of the system through line 95, input to the system through line 96 and the recycle acid with the new acid passed to pump 97 from where it is input to the reactor vessel through line 98. Pump 97 may not be necessary if the settler is elevated. The hydrocarbon effluent from the settler 93, including excess isoparaflinic hydrocarbons and alkylate is passed through line 99 in heat exchange with the olefin feed through line 101 after heat exchanger 1% to neutralization shown schematically at 102. From the neutralization step, line m3 passes the hydrocarbon eflluent to heat exchanger 1414 where steam or other heating medium flowing through line 1115 heats the hydrocarbon eflluent to drive olt isoparaffin-ic hydrocarbons therefrom. The heated effluent is then passed through line 106 to effluent flash drum 107. The vapors evolved at the heat exchanger 104 are drawn off from the flash drum through line 108, passed to condenser 109 and from thence through line 110 to accumulator 111. From accumulator 111, line 112 passes to pump 113 from which eflluent line 114 recycles the isobutane to main feed line 89 and from thence into the reactor. Accumulator 111 and pump 113 may not be necessary in some installations as in almost all cases the operating pressure of the effluent flash drum will be high enough to force the condensate back to the reactor without requiring a pump.

The heated, vapor withdrawn, hydrocarbon effluent is then taken off the bottom of effluent flash drum through line 115a and passed to deisobutanizer tower 11511. A reboiler has output and return lines 1150 and 11501 to and from heat exchanger 1156 from the deisobutanizer tower. Normal butane, other paraflinic hydrocarbons and alkylate products are withdrawn from the system though line 1151 The overhead from the deisobutanizer tower, comprising isobutane and other hydrocarbons, is passed through line 115g to condenser 115k and from thence through line 116 to accumulator 117. From the accumulator 117, line 118 passes the condensed isobutane recycle to pump 119 from whence it may be recycled to the tower through line 120 or passed to recycle line 121 which joins main feed line 39 shortly before the reactor.

Generally speaking, the basic objective of the efliuent pressure flash system in the above (FIG. 2) system, the FIG. 1 system and those to be described, is to provide a simple means of increasing the quantity of isobutane recycle in an alkylation system without requiring the expansion of the deisobutanizer tower and its accessory equipment. In the efiluent flash vaporization system, the net hydrocarbon effluent from the reactor section, after heat exchange with the various feed streams, neutralization and water wash (optional), is heated under any desired pressure to a suitable temperature and the hot efliuent is discharged into a separating drum. When sufficient heat is applied to the eflluent, the temperature thereof will be increased to its boiling point at the operating pressure and, if additional heat is applied, vapors will be formed. In passing through the transfer line between the heater and separating drum, an equilibrium will be established between the liquid and the vapors and the latter may be withdrawn from the top of the separator. These vapors, in a normal alkylation system, will contain a high percentage of isobutane. In the systems shown, the vapors will be condensed in a normal manner and the condensate will be recycled to the alkylation reactor. The liquid remaining after the eflluent flash vaporization is charged to the deisobutanizer tower in the customary manner.

Comparing the FIG. 2 system with the FIG. 1 system, the same objects and advantages discussed apply, with the exception, of course, that in the FIG. 2 system, no vapors are evolved in the reaction zone. The efiiciency of the valve 171 and from treated in the same regulating valve 175) passed into line process is affected, however, by the isobutane concentration of the hydrocarbon liquid in contact with the catalyst. Again using a given deisobutanizer with a given overhead recycle rate, an eflluent flash system may be used to increase the equilibrium isobutane concentration in the reactor materially.

Referring to FIG. 3, the numbering therein will begin at 130 to avoid confusion with the previous described system. At 130 is shown the shell of a reaction vessel similar in construction and operation to that shown in FIG. 2 at 70. Circulating tube 131 has impeller 132 at one end driven by shaft 133 attached to motor 134. Heat exchanging tube bundle 135 extends into the other end of the open ended circulating tube and is received in tube sheet 136 which closes one end of header 137. Header 137 has bafile 138 therein dividing its volume between the inputs of the two sections of the tube bundle. Input connection 139 and output connection 140 connect with the two parts of the header 137 for the inlet and output of heat exchanging medium. This system is an effluent refrigeration alkylation system. Olefin is put into the system through line 141 which is joined by fresh isobutane feed line 142 after heat exchanging of the olefin feed. Main feed line 143 passes from the heat exchanging step to the reactor 130.

The reaction takes place in the reaction vessel as previously described relative reactor 70 and efiiuent is taken off from the vessel 130 through line 144, including acid, alkylate and excessive isoparafiins, which is passed to acid settler 145. Acid is taken oif from the settler through line 146, some acid is taken from the system through line 147 and fresh acid input to the system through line 148, the acid feed then passing to the reactor. The acid-free hydrocarbon efiiuent is then passed optionally into line 150 or line 151. Valves 152 and 153 regulate the direction of this flow. If passed through line 150, valve 152 and line 154, the hydrocarbon efiluent is pressure reduced at valve 153 and passed into the input fitting 139 by line 155. After the pressure-reduced, chilled, partially vaporized hydrocarbon eflluent passes through the tube bundle .135, it is passed through line 156 to suction trap 157. From the suction trap 157, vapors are taken olf the top through line 158, passed to compressor 159, through line 160 to condenser 161 and through line 162 from the condenser to accumulator 163. From accumulator 163, the isobutane condensation is passed through line 164 to join main feed line 143 for recycle to the reaction zone of the reaction vessel 130. Liquid is taken off the bottom of the suction trap 157 through line 165 and, passing to pump 166, is discharged therefrom through line 167 to heat exchanger 168 and from thence through line 169 to the neutralization step shown at 170 schematically.

Alternatively, if the hydrocarbon efiluent is passed through line 151 and valve 153, it is pressure reduced at thence passed through line 172 to the The liquid and vapors ultimately are manner as the liquid and vapors from the flow through line 150 but, in the absence of a circusuction tank 157.

lation pass through the heat exchanging coil 135 from line 150, liquid is drawn off through line 173 from the bottom of the suction trap (regulated by liquid level 174 155, recycled through the heat exchanging coil 135 and thence through line 156 back to the suction trap.

Independently of which previously described scheme of efiluent refrigeration flow is employed, the liquid from the suction trap drawn off through line 165 reaches the neutralization step at 170 and from thence passes through line 177 to heater 178 and from thence through line 179 to efiluent flash drum 180. Steam line 181 heats the hydrocarbon efiiuent passing through the heat exchanger or heater 178. From the effluent flash drum 180, line 182 passes the vapors to condenser 183 and from thence through line 184 to join the main feed line 143 to the reactor 130.

'The heated, vapor-Withdrawn, hydrocarbon effluent from the flash drum 180 is passed through line 189 to deisobutanizer tower 190. Normal butane, other hydrocarbons and alkylate are withdrawn from the deisobutanizer tower bottom by line 191 while the overhead from the tower passes through line 192, condenser 193, and line 194 to accumlator 195. From accumulator 195, the isobutane and isoparaflinic hydrocarbons pass through line 196 to pump 197 and thence to recycle line 198 which joins main feed line 143. Recycle to the deisobutanizer from line 198 may take place through line 199.

In the arrangement of FIG. 3, not only do the same general advantages previously discussed above relative the FIGS. 1 and 2 systems apply, but also the isobutane concentration in the reaction zone is increased by the retaining of the efiiuent refrigerant recycle in liquid phase.

Referring to FIG. 4, therein is shown a paired reactor system employing but a single fractionation unit to separate isobutane from the alkylate product from both reactors. The upper reactor or contactor in the figure utilizes a closed cycle refrigeration system to cool the reaction therein, while the lower reactor utilizes an efliuent refrigeration system for the same purpose. The first reactor may be coupled with the second to employ the efilucnt refrigeration system of the second to aid in the separation of the isobutane and alkylate product, but not necessarily. These latter alternatives will be described.

Referring to FIG. 4, the effluent refrigeration system of the lower contactor will be first described. At 260 is shown the shell of a reactor having circulating tube 201, impeller 202 on drive shaft 203, the latter driven by motor 204 through gear reduction 205. Extending into the other end of the circulating tube 261 from impeller 202 is heat exchanging tube bundle 206 rolled into tube sheet 207. Header 208 has dividing battle 239 therein with input and output feed fittings 219 and 211 thereon. The function and operation of contactor 2% is the same as that of contactors 70 of FIG. 2 and of FIG. 3 and thus will not be again described.

Olefin is fed into the system through line 212 which is joined by fresh isobutane feed line 212a. The reaction takes place in the contactor in a highly circulated mass passing through and around the circulating tube 201. The effluent acid catalyst, alkylate product and excess isoparai'finic hydrocarbons are withdrawn through line 213 and passed to acid settler 214. Acid is withdrawn from the bottom of the settler 214 through line 215. Some acid may be withdrawn from the system through line 216 while fresh acid may be added through line 217, the acid to the reactor being input through line 215. The hydrocarbon phase is taken off the top of the acid settler through line 218, then pressure reduced at pressure reduction valve 219, whereafter the chilled, partially vaporized hydrocarbon effluent from the settler 214 is passed through line 220 to the input side of header 208, then through the coils 296, out output fitting 211 and through line 221 to flash drum 222.

The closed cycle system refrigerated contactor operation will now be described. Contactor shell 223 encloses circulating tube 224, impeller 225 and heat exchanging tube bundle 226, the latter received in tube sheet 227. Header 228 has dividing baffle 229 and input and output fittings 230 and 231. Impeller 225 is mounted on shaft 232 driven by motor 233 through reduction gear 234. Once again, the operation of contactor 223 is the same as that of contactors 220, 130 and 70. Closed cycle cooling system on contactor 223 operates as follows: Heat exchanging medium is input through line 235 to the header 228 and withdrawn through line 236. The heat exchanging medium is then passed to compressor 237, thence through line 238 to condenser 239 and from there through line 240 to accumulator 241. Accumulator 241 discharges through line 242 to pump 243.

The effluent from the reactor, including acid catalyst, alkylate product and excess isoparaffinic hydrocarbons,

osa es is discharged through line 244 and passed to acid settler 245. In the settler the acid is separated from the hydrocarbon phase of the effluent and acid is discharged through line 246, some acid being taken out of the system as required by line 247. Additional acid may be added through line 248 and the acid input to the contactor is shown.

The hydrocarbon phase efliuent may take either of two optional paths. The efiiuent is discharged from the settler through line 249. If desired, the hydrocarbon phase effluent may be passed directly to neutralization through line 250 and valve 251. How-ever, alternatively, efliuent may be passed through line 252 and valve 253, as well as line 254, to join the hydrocarbon effluent discharged from the acid settler 214 of the other contactor system. This latter optional line of action will be traced before the first mentioned option.

If the hydrocarbon effluent from the closed cycle systern is added to line 218, it is pressure reduced at 219 and passed through the heat exchanging system of contactor 2% to flash drum 222. The additional quantity of liquid and vapor chilled hydrocarbon phase effluent aids in the heat exchanging of contactor 201. In the flash drum 222, vapors are withdrawn (largely of isoparaffinic hydrocarbons) through line 255, passed to compressor 256, thence through line 257 to condenser 258, and from there through line 259 to accumulator 260. From accumulator 26%, the condensed isoparaffinic hydrocarbons may be charged as feed through line 261 to the main input feed line for hydrocarbons 262 to contactor 223. Fresh olefinic hydrocarbons may be charged to line 262 through line 263 and fresh isoparaffinic hydrocarbons to the same line through line 264. Thus it is evident that the totality of separated isoparaffinic hydrocarbons in flash drum 222 may be charged as feed to the contactor 223. Optionally, the feed from line 261 may be split between line 262 to contactor 223 and line 212 to the contactor 290 through line 261a. The isobutane feed, of course, is used in both contactors to maintain the desired great excess of isobutane in the circulating reaction stages in the contactors.

Returning to flash drum 222, liquid bottoms therefrom are taken off through line 265, passed to pump 266 and from thence through line 267 to join line 268 passing from valve 251 through heat exchanger 269 and line 270 to a neutralization and water washing step shown schematically at 271. In the optional process which we are describing, when the total hydrocarbon effluents from settlers 245 and 214 are passed through the coil 206 to flash drum 222, it is evident that all of the liquid in the flash drum is now being passed to the neutralization step 271 from both contactors.

From the neutralization step, the liquid hydrocarbon phase efliuent is passed through line 272 to heater 273 and from thence through line 274 to efliuent flash drum 275. Vapors from drum 275 are taken off through line 276, passed to condenser 277 and from there through line 278 to accumulator 279. Line 280 takes the condensed isoparaflinic hydrocarbons from accumulator 279 and, as regulated by valves 281 and 282 on lines 283 and 284 respectively, regulates the recycle of the excessive isoparaflinic hydrocarbons through lines 285 and 286 baclg to the contactors 223 and 200. Bottoms from the effluent flash drum pass through line 287 to the deisobutanizer tower 288. The isobutane and other hydrocarbon vapors are taken off the top of the deisobutanizer through line 289, passed to condenser 290 and thence through line 291 to accumulator 292. Discharge from accumulator 292 passes through line 293 to pump 294 and thence through line 295 to recycle line 296 which joins line 280 before the alternate feed lines to the contactors 223 and 200. Normal butane and alkylate bottoms are taken off the deisobutanizer through line 297, recycle to the desiobutanizer tower from line 295 is regu lated by valve 298 on line 299.

rated In the alternative method to passing both the hydrocarbon phase effluents from the settlers 245 and 214 through the tube bundle of contactor 200, the valve 253 may be closed and all of the hydrocarbon phase effluent from settler 245 passed directly into line 250, through valve 251 and into the neutralization step 271. When this is done, only the hydrocarbon phase effluent from settler 214 passes to flash drum 222 and the separated vapors are passed through line 261 to the feed line 262 while the liquid passes through line 267 to line 268 and into the neutralization step, as well. Thus it is seen, in either option, the feed into the neutralization step is from both systems, the only difference being the passage or not of both hydrocarbon efiiuents through the effluent refrigeration step of contactor 200'.

Thus it will be seen that the invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter hereinabove set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. In a process of alkylating isoparaffinic hydrocarbons with olefinic hydrocarbons in the presence of an acid catalyst wherein the isoparaflinic hydrocarbons are contacted with the olefinic hydrocarbons in the presence of said acid catalyst in a reaction step and catalyst, excess isoparaffinic hydrocarbons and product are withdrawn from the reaction step, the acid catalyst is at least substantially separated from the product and excess isoparaffinic hydrocarbons before passing the product and excess isoparaflinic hydrocarbons as a combined hydrocarbon phase to a fractionation step the reaction step indirectly heat exchanged by a first cooling means, the improvement which comprises passing at least a substantial portion of the said catalyst separated hydrocarbon phase to a flash vaporization separating step different from said first cooling means prior to passage to said fractionation step with sufficient application of heat thereto before it leaves said flash vaporization separating step to evolve a substantial proportion of the isoparaflinic hydrocarbons therein in vapor form therefrom, separating the said isoparaflinic hydrocarbon vapors from the remaining hydrocarbon phase in said flash vaporization separating step, condensing the said separated isoparaflinic hydrocarbon vapors and recycling them as feed to the reaction step and then passing the remaining hydrocarbon phase from said flash vaporization separating step directly to said fractionation step and recycling additional isoparaflinic hydrocarbons from said fractionation step as feed to said reaction step.

2. In a process of alkylating isoparaffinic hydrocarbons with olefinic hydrocarbons in the presence of an acid catalyst, wherein the isoparaflinic hydrocarbons are contacted with olefinic hydrocarbons in a reaction vessel in the presence of the acid catalyst and an excess of the isoparaiflnic hydrocarbons, at least a substantial separation of acid is made in the reaction vessel from excess isoparaffinic hydrocarbons and reaction product, the sepaacid and some excess isoparafiinic hydrocarbons being separately withdrawn from the reaction vessel, and a hydrocarbon phase effluent containing reaction product and additional excess isoparaflinic hydrocarbons therein is withdrawn from the vessel and passed to a fractionation step, the improvement which comprises passing the said catalyst separated hydrocarbon phase effluent to a flash vaporization separating step prior to passage to said fractionation step with sufficient application of heat thereto before leaving said flash vaporization step to evolve a substantial proportion of the excess isoparafiinic hydrocarbons in vapor form therefrom, separating the said isoparaflinic hydrocarbon vapors from said hydrocarbon phase in said flash vaporization separating step, condensing the separated isoparaflinic hydrocarbon vapors from said flash vaporization separating step and recycling them as feed to the reaction vessel, passing the residual hydrocarbon phase from said flash vaporization separating step tosaid fractionation step and recycling additional isoparaflinic hydrocarbons from said fractionation step as feed to said reaction vessel.

3. In a process wherein isoparaflinic hydrocarbons and olefinic hydrocarbons are contacted with an acid catalyst in a reaction step, a mixture of hydrocarbons is withdrawn with acid catalyst as efliuent from said reaction step, the eflluent from said reaction step is separated into a hydrocarbon phase substantially free of acid catalyst and an acid phase, the reaction and catalyst separating steps are maintained under sufficient back pressure to keep all hydrocarbons in liquid phase, the pressure is reduced on the hydrocarbon phase in at least one evaporative cooling step to refrigerate the same and vaporize at least some isoparaflinic hydrocarbons therein, at least a portion of the pressure reduced hydrocarbon phase is passed in indirect heat exchanging relationship with the reaction step thereby vaporizing at least some additional isoparaflinic hydrocarbons, and the vaporized isoparaffinic hydrocarbons are separated from the liquid hydrocarbons in a first separating step, the improvement which comprises Withdrawing liquid hydrocarbons from said first separating step, passing said withdrawn liquid hydrocarbons to a flash vaporization separating step with a suflicient application of heat thereto before leaving said flash vaporization separating step to evolve a substantial proportion of any isoparaflinic hydrocarbons therein in vapor form therefrom, separating said evolved isoparaffinic hydrocarbon vapors from the remaining liquid hydrocarbon phase in said flash vaporization separating step, condensing the said separated isoparaflinic hydrocarbon vapors and recycling them as feed to the reaction step and then passing the liquid hydrocarbon phase from said flash vaporization separating step to a fractionation step and recycling additional isoparaflinic hydrocarbons from said fractionation step as feed to said reaction step.

4. In a combination process of effluent refrigeration and closed cycle refrigeration applied to alkylation processes wherein isoparaflinic hydrocarbons and olefinic hydrocarbons are contacted with a liquid acid catalyst in a first and a second reaction step, wherein said first reaction step is heat exchanged with a closed cycle refrigeration system, eflluent reaction mixtures are discharged from said first and second reaction steps, said effluent re action mixtures are separated into hydrocarbon phases substantially free of acid catalyst and acid phases, pressure is reduced on said hydrocarbon phases to vaporize excess isoparaffinic hydrocarbons therein, and at least a major portion of the pressure reduced combined hydrocarbon phases are passed in indirect heat exchanging relationship with the second reaction step, the said combined heat exchanged hydrocarbon phases and any pressure reduced nonheat-exchanged hydrocarbon phases are passed to a first separating step, and the pressure reduced hydrocarbon phases are there separated into liquid and vapor components, the improvement which comprises withdrawing liquid hydrocarbon phase from said first separating step, passing said withdrawn hydrocarbon phase to a flash vaporization separating step with sufficient application of heat thereto before leaving said flash vaporization separating step to evolve a substantial proportion of the isoparaflinic hydrocarbons therein in vapor form therefrom, separating the said isoparaifinic hydrocarbon vapors from said hydrocarbon phase in said flash vaporization separating step, condensing said vapors and recycling them as feed to at least one of said reaction steps, then passing the liquid hydrocarbon phase from said flash vaporization separating step to a fractionation step and recycling additional isoparaflinic hydrocarbons from said fractionation step as feed to said reaction step.

5. The improvement in treating the substantially catalyst separated hydrocarbon phase effluent from an alkylation reaction step wherein isoparafiinic hydrocarbons were alkylated with olefinic hydrocarbons in the presence of an acid catalyst prior to passage of the said hydrocarbon phase to a fractionation step to seyarate excess isoparaflinic hydrocarbons therefrom for recycle to said reaction step, the said hydrocarbon phase eflluent including alkylate product and excess isoparaflinic hydrocarbons separated from the acid catalyst, the said alkylation reaction step heat exchanged to control the temperature thereof, comprising the steps of passing a substantial portion of said hydrocarbon phase effluent including alkylate product and excess isoparaflinic hydrocarbons to a flash vaporization separation step, which separating step is independent of any means heat exchanging the reaction step with suflicient application of heat thereto before leaving said flash vaporization separating step to evolve a substantial proportion of the isoparafiinic hydrocarbons therein in vapor form therefrom, separating said isoparaffinic hydrocarbon vapors from said hydrocarbon phase eflluent in said flash vaporization separating step, condensing the said isoparaflinic hydrocarbon vapors and recycling them as feed to the alkylation reaction step, then passing the liquid hydrocarbon phase from said flash vaporization separating step to a fractionation step and recycling additional isoparaflinic hydrocarbons from said fractionation step to said alkylation reaction step as feed.

References Cited in the file of this patent UNITED STATES PATENTS 2,008,578 Cooke July 16, 1935 2,412,143 Gorin et al. Dec. 3, 1946 2,429,205 Jenny et a1. Oct. 21, 1947 2,457,564 Kniel Dec. 28, 1948 2,664,452 Putney Dec. 29, 1953 2,818,459 Gantt Dec. 31, 1957 2,906,796 Putney Sept. 29, 1959 OTHER REFERENCES Goldsby et al.: The Oil and Gas Journal, vol. 54, No. 20, pages 104-107, Sept. 19, 1955. 

5. THE IMPROVEMENT IN TREATING THE SUBSTANTIALLY CATALYST SEPARATED HYDROCARBON PHASE EFFUENT FROM AN ALKYLATION REACTION STEP WHEREIN ISOPARAFFINIC HYDROCARBONS WERE ALKYLATED WITH OLEFINIC HYDROCARBONS IN THE PRESENCE OF AN ACID CATALYST PRIOR TO PASSAGE OF THE SAID HYDROCARBON PHASE TO A FRACTIONATION STEP TO SEYARATE EXCESS ISOPARAFFINIC HYDROCARBONS THEREFROM FOR RECYCLE TO SAID REACTION STEP, THE SAID HYDROCARBON PHASE EFFUENT INCLUDING ALKYLATE PRODUCT AND EXCESS ISOPARAFFINIC HYDROCARBONS SEPARATE FROM THE ACID CATALYST, THE SAID ALKYLATION REACTION STEP HEAT ECHANGE TO CONTROL THE TEMPERATURE THEREOF, COMPRISING THE STEPS OF PASSING A SUBSTANIAL PORTION OF SAID HYDROCARBON PHASE EFFUENT INCLUDING ALKYLATE PRODUCT AND EXCESS ISOPARAFFINIC HYDROCARBONS TO A FLASH VAPORIZATION SEPARATION STEP, WHICH SEPARATING STEPS IS INDEPENDENT OF ANY MEANS HEAT EXCHANGING THE REACTION STEP WITH SUFFICIENT APPLICATION OF HEAT THERETO BEFORE LEAVING SAID FLASH VAPORIZATION SEPARATING STEP TO EVOLVE A SUBSTANTIAL PROPORTION OF THE ISOPARAFFINIC HYDROCARBONS THEREIN IN VAPOR FORM THEREFROM, SEPARATING SAID ISOPARAFFINIC HYDROCARBON VAPORS FROM SAID HYDROCABON PHASE EFFUENT IN SAID FLASH VAPORIZATION SEPARATING STEP, CONDENSING THE SAID OSPARAFFINIC HYDROCARBON VAPORS AND RECYCLING THEM AS FEED TO THE ALKYLATION REACTION STEPS, THEN PASSING THE LIQUID HYDROCARBON PHASE FROM SAID FLASH VAPORIZATION SEPARATING STEP TO A FRACTIONATION STEP AND RECYCLING ADDITIONAL ISOPARAFFINIC HYDROCARBON FROM SAID FRACTIONATION STEP TO SAID ALKYLATION REACTION STEP AS FEED. 